Four 18GB 10000rpm and one 40GB 7200rpm drive in my machine. Assorted drives in other machines around the house include: two 18GB 10000rpm, a 9GB 10000rpm, a 30GB 7200rpm, a 20GB 7200rpm, a 40GB 5400rpm, and an 8GB 5400rpm.
I'm nowhere near filling up all of the space in my machine, and all of the other machines around the house probably have less than 25% of their total disk space filled. I frequently burn things to CD though, for some reason I just feel the need to keep data off my drives.
